Communications device, an access point and methods therein for accessing a resource unit

1. A method performed by a communications device for accessing a Resource Unit, RU, wherein the communications device and an Access Point, AP, are operating in a wireless communications network, and wherein the method comprises: making a determination whether to start an access attempt within a time interval or instead to start the access attempt outside the time interval, wherein the time interval is known to both the communications device and the Access Point; when the determination has been made to start the access attempt within the time interval, randomly selecting a counter value from a first range given by zero and a first Contention-Window OFDMA, CWO, value CWO 1 ; when the determination has been made to start the access attempt outside the time interval, randomly selecting the counter value from a second range given by zero and a second CWO value CWO 2 , wherein the second CWO value CWO 2 is larger than the first CWO value CWO 1 ; performing a contention procedure using the selected counter value, wherein a Resource Unit, RU, is accessed in dependence of the performed contention procedure.

2. The method of claim 1 , wherein the performing of the contention procedure comprises: receiving, from the AP, first information about a first number of available RUs; when the randomly selected counter value is equal to or lesser than the first number of available RUs, accessing one RU among the first number of available RUs for transmission; and when the randomly selected counter value is larger than the first number of available RUs, deferring from accessing.

3. The method of claim 2 , wherein the performing of the contention procedure further comprises, when the randomly selected counter value is larger than the first number of available RUs: decrementing the randomly selected counter value with the first number of available RUs; receiving, from the AP, second information about a second number of available RUs; when the decremented counter value is equal to or lesser than the second number of available RUs, accessing one RU among the second number of available RUs for transmission; and when the decremented counter value is larger than the second number of available RUs, deferring from accessing.

4. The method of claim 1 , wherein the time interval is given by (T 0 +nT)±δ wherein T 0 is a start point of time, T is a number of time units between two consecutive time intervals, n is a non-negative integer, and 2δ is a length of the time interval, wherein δ<<T.

5. The method of claim 1 , wherein the time interval is obtained by: transmitting, to the AP, a request to access a RU for transmitting data at points in time spaced apart by T time units; and receiving, from the AP, information relating to the start point of time T 0 , the first CWO value CWO 1 and the δ of the time interval.

6. The method of claim 1 , further comprising: entering an inactive mode between a first access attempt and a second access attempt.

7. The method of claim 1 , further comprising: determining to perform an access attempt outside the time interval when such an access attempt is more power efficient than a transmission attempt within the time interval.

8. A communications device for accessing a Resource Unit, RU, wherein the communications device and an Access Point, AP, are configured to operate in a wireless communications network, and wherein the communications device is configured to: make a determination whether to start an access attempt within a time interval or instead to start the access attempt outside the time interval, wherein the time interval is known to both the communications device and the Access Point; when the determination has been made to start the access attempt within the time interval, randomly select a counter value from a first range given by zero and a first Contention-Window OFDMA, CWO, value CWO 1 ; when the determination has been made to start the access attempt outside the time interval, randomly select the counter value from a second range given by zero and a second CWO value CWO 2 , wherein the second CWO value CWO 2 is larger than the first CWO value CWO 1 ; perform a contention procedure using the selected counter value, wherein a Resource Unit, RU, is accessed in dependence of the performed contention procedure.

9. The communications device of claim 8 , wherein the communications device is configured to perform the contention procedure by further being configured to: receive, from the AP, first information about a first number of available RUs; when the randomly selected counter value is equal to or lesser than the first number of available RUs, access one RU among the first number of available RUs for transmission; and when the randomly selected counter value is larger than the first number of available RUs, defer from accessing.

10. The communications device of claim 9 , wherein the communications device is further configured to perform the contention procedure by further being configured to, when the randomly selected counter value is larger than the first number of available RUs: decrement the randomly selected counter value with the first number of available RUs; receive, from the AP, second information about a second number of available RUs; when the decremented counter value is equal to or lesser than the second number of available RUs, access one RU among the second number of available RUs for transmission; and when the decremented counter value is larger than the second number of available RUs, defer from accessing.

11. The communications device of claim 8 , wherein the time interval is given by (T 0 +nT)±δ wherein T 0 is a start point of time, T is a number of time units between two consecutive time intervals, n is a non-negative integer, and 2δ is a length of the time interval, wherein δ<<T.

12. The communications device of claim 8 , wherein the time interval is obtained by the communications device being configured to: transmit, to the AP, a request to access a RU for transmitting data at points in time spaced apart by T time units; and receive, from the AP, information relating to the start point of time T 0 , the first CWO value CWO 1 and the δ of the time interval.

13. The communications device of claim 8 , further being configured to: enter an inactive mode between a first access attempt and a second access attempt.

14. The communications device of claim 8 , further being configured to: determine to perform an access attempt outside the time interval when such an access attempt is more power efficient than a transmission attempt within the time interval.

15. A nontransitory computer readable storage medium comprising a computer program, comprising instructions which, when executed on at least one processor, causes the at least one processor to carry out a method of a communications device for accessing a Resource Unit, RU, wherein the communications device and an Access Point, AP, are operating in a wireless communications network, and wherein the method comprises: making a determination whether to start an access attempt within a time interval or instead to start the access attempt outside the time interval, wherein the time interval is known to both the communications device and the Access Point; when the determination has been made to start the access attempt within the time interval, randomly selecting a counter value from a first range given by zero and a first Contention-Window OFDMA, CWO, value CWO 1 ; when the determination has been made to start the access attempt outside the time interval, randomly selecting the counter value from a second range given by zero and a second CWO value CWO 2 , wherein the second CWO value CWO 2 is larger than the first CWO value CWO 1 ; performing a contention procedure using the selected counter value, wherein a Resource Unit, RU, is accessed in dependence of the performed contention procedure.